Television station selector



A. W. FRANKLIN TELEVISION STATION SELECTOR May 25, 1954 5 Sheets-Sheet 1Filed Aug. 21, 1948 INVENTOR ALBERT W. FRANKLIN Q ATT RNEYZLZ May 25,954 A. w. FRANKLIN 2,679,596 TELEVISION STATION SELECTOR Filed Aug. 21,1948 3 Sheets-Sheet 2 INVENTOR ALBERT W. FRANKLIN ATTO R N EYS -Y 25,1954 A. w. FRANKLIN 2,679,596

TELEVISION STATION SELECTOR Filed Aug. 21, 1948 ssheets-sneet s Tici. S-

INVENTOR ALBERT W. FRANKLEN Patented May 25, 1954 UNITED STATES FATENTOFFICE TELEVISION STATION SELECTOR Albert W. Franklin, New York, N. Y.

Application August 21, 1948, Serial No. 45,473

3 Claims. 1

This invention relates to improvements in selector switches andassociated circuits by means of which electrical apparatus andparticularly short. wave high frequency apparatus such as televisionreceivers may be tuned.

An object of this invention is to provide an improved form of switchingmeans and associated circuits for selectively tuning a multichanneltelevision receiver to any one of a number of desired predeterminedchannels.

A more specific object of the invention is to provide a station selectorsuch as the above in the form of a push button mechanism.

Another object of the invention is to provide a station selector such asthe above in the form of a rotary switch.

A more detailed object of the invention is to provide an improved novelform of high frequency transmission circuit for electrical apparatussuch as a television receiver and manual means for selectively tuningthat circuit to a plurality of different frequencies.

Still another object of the invention is to provide in a radio apparatusof this type a novel form of high frequency circuit simultaneouslyformed and attached to a supporting panel by stamping it from a metalsheet superposed on said panel.

A still more specific object of the invention is the provision ofinductances associated with such a circuit and similarly made.

A broader object of the invention is the provision of high frequencytransmission circuits for apparatus of this type in such form as toadapt them to mass reproduction while maintaining the necessary rigidelectrical tolerances required.

A still more specific object of the invention is the provision of novelground circuits for such transmission circuits and/or switching meansfor selectively connecting predetermined frequency points of saidcircuit to ground to complete it and thereby tune the equipment to adesired.

frequency channel.

Other and more detailed objects of the invention will be apparent fromthe following description of several embodiments thereof as illustratedin the attached drawings.

In the accompanying drawings- Figure 1 is a top plan view of onephysical embodiment of the subject matter of this invention as employedin a push button actuated frequency selector;

Figure 2 is a bottom plan view of a portion of the mechanism of Figure1;

Figure 3 is a cross sectional view taken on the line 3-3 of Figure 2;

Figure 4 is a cross sectional view taken on the line il of Figure 3;

Figure 5 is a side elevational view of the embodiment of the inventionin a rotary switch;

Figure 6 is a view of the device from the plane 3-5 as indicated inFigure 5;

Figure I is a plan view from the plane 'i'--l as indicated in Figure 5;

Figure 8 is. a detailed cross sectional view showing the switch rotorand operating shaft;

Figure 9 is a plan view of the stator plate of the oscillator trimmercondenser; and

Figure 10 is a similar view of the rotor of the oscillator trimmercondenser.

The subject matter of this invention will be explained in connectionwith the control mech anism for a television receiver but those skilledin the art will recognize that much of the subject matter hereindisclosed is applicable to other electrical circuits and particularlyvery high frequency circuits.

Continuing reference, for disclosure purposes, to television receivers,one of the chief components thereof is the station selector which shouldbe of such construction as to permit reproduceability within therequired close limits in the values of inductance, resistance andcapacity. The present methods of constructing apparatus of this type arenot adapted to uniformity in mass production methods because of thedifficulty of maintaining these values within the close tolerancesrequired.

Most commonly today, the apparatus is adapted for operation at thevarious television channel frequencies by the use, among other things,of wound inductances, each being tuned to the individual frequency ofthe associated channel. Those skilled in the art appreciate the extremedifiiculty of attaining the required inductive values with wire woundinductances. Much difficulty is encountered in maintaining the requiredclose inductance tolerance in mass producing equipment of this type.Indeed, it is safe to say that it is almost impossible to maintainuniformity in production so that each set requires individualadjustment, greatly increasing the cost of production.

Additionally, equipment of this type is particularly vulnerable tochanges in temperature, humidity, relative position of parts withrespect to each other and other variable conditions dilicult to control.By means of the novel subject values are held within their close limits.

signing the transmission line allowance can be 3 matter hereindisclosed, all of these difiiculties are easily overcome.

As illustrated in the drawings, the subject matter of this invention hasbeen exemplified by application of two types of channel selectors, oneemploying push buttons and the other a rotary switch of the typegenerally employed at the present time in television receivers. In thepush button type, as illustrated, three transmission lines (more may beused if necessary) are simultaneously formed and attached to aninsulating panel by shearing or cutting them from a sheet of metalsuperposed on the support. These transmission lines may be attached bythe clinching action resulting from stamping them from the metal sheetbut when required additional attachment may be effected by using asuitable adhesive and if necessary a hot stamping die to enhance theadhesive action of the cement which is used. Many types of adhesives orcements are available for the purpose, including the thermoplastic andthermosetting types of adhesives, as those skilled in the art willunderstand. By stamping the transmission circuits from a metal sheet inthe manner described, it is possible when a properly designed cuttingdie is employed, to insure exact uniformity and reproduceability of thecircuits in quantity. An important advantage of such procedure is toinsure that the exact desired form of circuit will be produced with theparts in the exactly desired relative position. Furthermore, by thusattaching them to the supporting panel these conditions are maintainedthroughout the useful life of the structure.

In order to attain the desired low inductance values required, thetransmission line is provided with taps in the form of contacts, one foreach of the frequency channels to which the transmission line is to betunable. To further assure the desired low inductance values, thecontacts which form the taps are made of relatively heavy metal Withrespect to the metal of the transmission line thereby assuring that thelow inductance In demade for the inductance of the contacts so that thefinished circuit can be tuned to the desired frequency with the requiredaccuracy.

Further contributing to a low inductance circuit, a low inductanceground is provided and switch contacts are arranged to connect thevarious taps selectively to this ground by a very short connection.

It is desired to emphasize that in the case of a plurality oftransmission lines it is necessary that they bear in each case the samerelationship to each other in physical spacing so that intercircuitvalues such as intercircuit capacity coupling and electrostatic couplingwill be the same. To accomplish this object, the plurality of circuitsare stamped simultaneously from a single sheet of metal andsimultaneously attached to the support so that the desired spatialrelationship is assured with a properly designed coating die.

In the station selector illustrated, three transmission circuits areprovided. One provides the oscillator circuit, another the convertercircuit, and the third a radio frequency circuit. Additional radiofrequency circuits may be added when required. In the push button androtary types illustrated, the taps of each of these circuitscorresponding, for example, to a particular television channel, may bedirectly connected to associated ground circuits simultaneously, so thatby a single operation all of these circuits are simultaneously tuned tothe same television channel.

The ground straps which may also be stamped to exact size are attachedon the back of the channel and are so aligned with their associatedtransmission circuits attached to the front that they act as part of thetuned circuits, thereby giving a higher ratio of inductance to capacityto assure higher gain and amplification as is well understood in thisart.

In order to provide lower inductance to ground, additional groundcircuits can be stamped on the top of the panel in the same way as arethe transmission circuits and connected to the ground straps at the backof the panel electrically and mechanically by means of rivets or eyeletswhich interconnect them.

In order to compensate for variation in vacuum tube capacitance used insuch circuits, it is desirable to provide for small adjustment of theinductance of the associated transmission lines. This is accomplished byproviding large flat head screws which are associated with thetransmission line and adjustable with respect thereto to provide thenecessary compensation.

The manner in which the above objects and functions are attained willfirst be described in connection with Figures 1 to l, inclusive, whereina television push button selector switch including the associatedtransmission lines is illustrated. In the form shown it includes achassis consisting of a base plate I having a large opening 2 thereinand provided with integral upturned end Walls 3. A series of side wallsl, 5 and B are attached to the base plate and between the end walls toprovide a flat rectangular housing, a portion of the top of which isclosed by means of two plates 5' and 8, of insulating material. Theseplates are respectively secured to the chassis by means of the screws 9and it. The insulating plate sections i and 8 can be in a single piece,if desired, but in some cases stamping of the attached parts isfacilitated by making it of two parts. Mounted on the plate 8 are thevacuum tube sockets l l, I2 and 13 which in the case illustrated areadapted to receive the oscillator, converter and high frequency tubesrespectively used in such a device.

Attached to the insulating panel 1 are the three transmission lines I9,20 and 2| integral with which and formed simultaneously therewith bystamping are the spiral inductances l4, l5 and I6, respectively, and asshown, the rectangular extensions 22, I22 and 222. The configuration ofthese three transmission lines is determined by the electricalcharacteristics and spatial conditions permissible. These transmissionlines are provided with taps or lateral extensions upon which aresuperposed the relatively heavy metal contacts 59 2c and 2 lrespectively, which are secured to the panel I and mechanically andelectrically engaged with the side extensions of the transmision linesby means of rivets or eyelets i9 28*, and Zl The inductances it, it; andIt are adjustable by means of large. flat metal head screws of which twoare illustrated at H and i8. These screws threadedly engage at aperturesat the center of the spiral inductances and can be longitudinallyadjusted by turning. The transmission line 22 terminates at an eyelet 23which extends through the panel l7 and is electrically in contact withthe ground strip 33 as illustrated in Figure 2. A pair of metal groundplates 23 and 25 are attached to the panels 7 and 8 by means of eyeletsor rivets. In the case of the ground plate 25, its attaching eyelets 2ealso electrically and mechanically engage the ground strip 23, seeFigure 2. In the case of the ground strip 23, the eyelets 34electrically and mechanically engage the ground strip and the eyelets35' electrically and mechanically engage the ground strip 35. Thoseterminals of the sockets ll, [2 and I3 which require grounding areprovided with ground tabs li i2 12 it i3 and 13 which may be for examplesoldered to the ground strips 23 and 25, as illustrated.

The push button levers are illustrated at 2'! to 21, inclusive. Therotary manual 26 is provided to adjust the oscillator circuit trimmercondenser and in this form of device there are no features of noveltydisclosed in connection therewith and so no further reference theretowill be made. It

will also be understood that there is additional equipment within thechassis associated with the manual .25 and the tube sockets II, I2 andI3 but they are not illustrated and no further reference thereto isdeemed necessary.

The manuals fil to 21 consist of metal bars with finger buttons on theexposed ends which bars are mounted for longitudinal sliding movement inthe chassis housing as will be clear from Figures 2 and 3. Each thereofcorresponds to a frequency channel to which the equipment is tunable. isclear from Figure 4, each of the contacts 55 Titl and 2 l consists ofright angle metal pieces, the short arm of which, as is clear fromFigure l, overlies a lateral extension integral with the portions [9, 2tand ii of the transmission circuit while the longer extension. projectsthrough a rectangular opening in the panel 7 so as to provide three rowsof contacts as will be clear from the drawings extending parallel to theground strips 33, E4 and 35, respectively, but spaced a short distancetherefrom. These ground strips are provided with upturned taps 33 34 and35 which are aligned with the contacts [9 23 and Zi respectively, as isclear from Figures 2 and 3.

Although not part of this invention, the interconnecting mechanismbetween the push button rods having been illustrated, it will bedescribed. As shown in Figure 3, each rod is provided with a cam shapednotched projection 28, attached to cooperate with a latching bar 3|which is pivotally mounted on a pair of brackets 30, see Figure 1,attached to the bottom wall of the chassis. The free edge of the latchbar 3! is held down by means of a tension spring 32 anchored to thebottom wall 3| as shown and each of the push button bars has acompression spring 29 mounted on it so as to lie between the side wall 6and the lateral projection 23. When a button is pushed toward thechassis, the notched camming projection 23 rides under the latch bar 3!and spring 29 is compressed. Spring 32 resists the clockwise movement ofthe latch bar 3 l Figure 3, under the action of the camming projection28 so that as soon as the notch thereof comes under the edge of thelatch bar, spring 32 will pull it down into the notch, holding the pushbutton bar in actuated position. When any other push button bar of thegroup is later pushed inwardly its carnming projection 28 will raise thelatch bar against the resistance of spring 32 so that spring 29 of thepreviously actuated push button bar may return it to normal positionwhile the latch bar latches in actuated position the other push buttonbar. Thus, as is Well 6 understood in this art, upon actuation of anypush button a previously actuated button will be released to be returnedto normal position so that the circuits can be tuned to only onefrequency channel at a time.

Each of the push button bars as, for example, bar 21 is provided withthree substantially U- shaped contacts a, Z) and c, which are made ofthin spring metal and are generally U-shaped. They are slipped over thebar El so that it nests in the bases thereof and they are attachedthereto by means of eyelets or rivets, as shown. The extending arms ofthese contacts are slotted to provide two pairs of cooperating springfingers which are transversely curved as shown in Figure 4. Thesecontacts are attached to the bars such as the bar 21 in such a relativeposition that when the bar is unactuated, that is in the position shownin the drawings, these contacts will engage the tabs 33*, 34 and 35respectively, as shown in Figure 3, and when they are in actuatedposition these contacts will interconnect these same tab with theterminals it, 241 and 2H, respectively. The result is that the threetransmission circuits in the output circuits of the tubes in the socketsii, ill and i3 will be active up to the taps corresponding to theparticular push button rod which has been actuated. By way of example,if push button rod Zl has been actuated, the transmission circuits i9,29 and 2! will be active up to the first tap-cit terminal of each ofthese circuits which will be respectively grounded by the contacts a, band c to the ground strips 33, 3 5 and 35. Similarly, the actuation ofany one of these push button rods will return the previously actuatedrod to inactive position and complete the transmission circuits up tothe tap-off points corresponding to the terminals Mi 29 and 2 iassociated with the particular actuated rod. The grounding of each ofthe transmission circuits takes place simultaneously by the singleactuation of a particular button as will now be apparent. Thus, in thecase described the oscillator, converter and high or radio frequencycircuits will be completed to ground.

The same principles as previously illustrated have been incorporated inthe rotary switch of Figures 5 to 10, inclusive. One suitable form ofrotary switch is shown in Figure 5 which includes a cage or supportcomp-rising the insulating plates ll, 42, 43 and 41! secured together inspaced parallel relation by a suitable number of longitudinal traps e9.Journalled in suitable bearings in this structure is a longitudinallyextending and centrally placed shaft 55 preferably of noncircular crosssection to the end of which is secured an operating knob Attached to theshaft 45 adjacent the knob is a C-washer 49 located on the shaft andagainst which a second operating knob or wheel ll rests. The knob ll isconnected to a sleeve M which is rotatably mounted on the shaft 45 andhas secured at its far end a rotor plate of insulating material whichhas secured on one face thereof a metal plate or foil Eli which isattached thereto in any suitable manner as by stamping and cementing, aspreviously explained with respect to the transmission circuits. Attachedto the end plate ll are standards 53 which in turn support an insulatedstator 52 to which in turn are secured a pair of metal plates or foils52 attached in the same way for example. Interposed between the stator'52 and the sleeve 48 is a dished spring washer 5B which holds the parts41, 48 and SI against the spacing washer 49 to hold the rotor a desireddistance from the stator 52. The elements 5! and 52 provide a trimmercondenser which is to be connected in the output circuit of theoscillator to provide the necessary fine frequency adjustment for thatcircuit in an inexpensive form and convenient location with re spect tothe main tuning knob 46.

Figures 6 and 7 show the opposite sides of the wafer 42 which isgenerally similar in construction to the wafers 43 and 44 representingthe three transmission circuits illustrated for the rotary type ofswitch. As illustrated in Figure 6, the transmission circuit includes anintegral stamped spiral inductance 54, an arcuate conductor 55, a spiralinductance 56, a U-shaped inductance 51 and the spiral inductances 58,60 and 6|. As illustrated, the inductances 56, 51, 58 and 66 are notintegral with each other and the arcuate conductor 55 although theymight be so as to be stamped simultaneously. In the case illustrated,the outer end of inductance 56 is connected to the strip 55 by means ofa connector 56 on the back of the panel and its inner end is connectedon the back of the panel to one terminal of the inductance 57 by mean ofthe connector 56 The center of inductance 58 is connected on the back ofthe panel to the outer terminal of inductance 60 by means of a connector56. The center of inductance 66 is connected on the back of the panel tothe outer terminal of inductance 6! and its inner end terminal in turnis connected on the back of the panel by means of a connector 56 to oneof the contacts 66. The connectors 56 to 56 may be stamped onto the backof the panel similarly to the previous description for such forming andattaching operations and be connected through to the corresponding partson the front of the panel by means of rivets or eyelets a shown. Aseries of taps arranged concentrically and mechanically, andelectrically connected to the arcuate strip 55 by eyelets 66 are shownat 6B. These taps are in the form of pairs of spring contact fingersbetween which a radial tab 68*- on the metal ring 68 may pass. Thespiral inductance may be adjusted as before by means of fiat headedscrews as in the case of screw 62 illustrated for inductance 64.

The ring 68 is attached to an insulating rotor 61 which is mounted onthe shaft 45 for rotation therewith. On the opposite side of the rotor67 is another metallic ring 69. Rings 68 and 69 are attached to theinsulating rotor in any suitable manner as, for example, by the inwardlyradially projecting tabs 69b and 691) shown in each case. The rings 68and 69 are electrically connected together in any suitable manner, asfor example by means of a drop of solder (not shown), which wouldcross-connect an adjacent pair of tabs 68 and 69. Attached to the backof the panels are several spring clips 70 which engage the ring 69 andmake permanent contact therewith. These contacts in turn are connectedto a ground plate ll attached to the back of the panel as shown inFigure 7.

As will be apparent in view of all the foregoing it will be seen that asthe knob 46 is rotated rotor 67, with its attached rings 68 and 69, willturn with it. As these rings are electrically connected whenever the tabof ring 68 engages one of the contacts 60 it will be seen that thetransmission circuit including the parts 54, 55, 55, 57, 58, 66 and 6|will be tapped oil to the ground plate H so that in the case illustratedthe switch is adapted to a twelve channel or frequency televisionreceiver, for example. As the rotor moves in a clockwise direction,Figure 6, from the position shown, around a complete circle any one ofthe twelve taps may be engaged to tune the circuit to any one of thetwelve frequencies. The construction for the wafers 42 and 44 is thesame as that of wafer 43, so that all three transmission circuits aresimultaneously tuned to the same frequency.

As in the case of the push button type all of the metal parts with theexception of the contact 66 may be stamped onto the wafers on one orboth sides by a cutting die of predetermined design so that greatuniformity of reproduction can be effected between the electricaltolerance limits required for very high frequency circuits. Thus,uniformity and low cost is attained in a practical manner.

In view of the above description it will be apparent to those skilled inthe art that the subject matter of this invention is capable ofconsiderable variation and I do not therefore desire to be limited tothe illustrative embodiments herein disclosed but only as required bythe claims granted me.

What is claimed is:

l. A television station selector unit comprising a chassis having aninsulating support mounted thereon, a set of three inductivesubstantially planar circuit conductors attached to one side of saidinsulating support, a set of three substantially planar conductors to begrounded attached to the other side of said insulating support andelectrically associated respectively with said circuit conductors toprovide conductor pairs, said conductor pairs providing oscillator,converter and high frequency transmission circuits, a plurality of tapsfor each of said circuit conductors and means for simultaneouslyselectively connecting said taps of each circuit conductor to theassociated ground conductor respectively.

2. In the combination of claim 1, each of said conductor pairs havingcontacts aligned respectively in pairs and said means simultaneouslyinterconnecting the corresponding ground and circuit conductor contactsof each of said three circuits.

3. In the combination of claim 1, each of said circuit conductorsincluding a multi-turn planar inductance, said selecting means adjustingthe inductance thereof.

References Cited in the file Of this patent UNITED STATES PATENTS NumberName Date 1,395,390 Clement Nov. 1, 1921 2,062,253 Walker et al -1 Nov.24, 1936 2,092,069 Hollmann Sept. 7, 1937 2,183,723 Paschke Dec. 19,1939 2,414,280 Thomas Jan. 14, 1947 2,423,152 Mitchell July 1, 19472,474,988 Sarbrove July 5, 1949 2,497,747 Valdettaro Feb. 14, 1950FOREIGN PATENTS Number Country Date 103,948 Australia May 26, 1938 OTHERREFERENCES Electronics for September 1948, pages 76-79. Television FrontEnds by Sobel.

